Muck fires often occur during times of drought, when water tables are low, and as the result of a forest fire. The heat from above causes the loosely packed layer of peat, located below the soil, to catch fire. Oxygen seeps through the soil, and the fire smolders for days.
Muck contains organic debris from plants and organisms. Usually, these carbon compounds account for more than one-third of the soil. Normally, muck is located at the bottom of swamps and remains wet, so it does not burn.
When rain is scarce, ground water dries, exposing the muck to the air and drying it so that it's flammable. When ignited, the heat of a muck fire dries the roots of trees and other vegetation. Losing the support of roots causes trees to fall to the ground, where the heat of the fire beneath them ignites them and continues to spread the fire. As the muck burns, the soil levels drop, and areas that were once swamps become lakes and ponds.
Muck fires are difficult to stop, requiring large amounts of water. Once started, they usually burn as deep as the muck itself. Often, rain is the only way a muck fire is extinguished, although firefighters plow firebreaks and till the ground to find any hot spots.